a. Field of the Invention
This invention relates to an apparatus for obtaining representative samples of sediment from stream beds, river beds, lake beds, and the like. More specifically, it relates to an apparatus containing a cryogenic probe which freezes portions of stream beds (the term "stream beds" will be used herein to include river beds, lake beds, and the like). These frozen portions cling to the probe and are easily removed from their environment.
B. Description of the Prior Art
Determining the effects of industrialization, mining, farming, road building, logging, etc., on the surrounding environment is important in future planning of these and other vital industries. Of particular importance to the fishing industry are programs designed to detect environmental changes in streams, rivers, lakes, bays, etc., used by spawning salmon and the like. Many of these changes are small, and sensitive techniques are needed to detect them.
Apparatuses for sampling stream bed sediments described in the literature have not generally been adequate.
One such device consists of an open-ended tube surrounded by a closable, cooling jacket into which is placed dry ice and n-butyl alcohol. The device containing the coolant is allowed to settle into the muddy sediment at the bottom of a lake. After several minutes the device containing the frozen core is lifted to the surface (J. Shapiro, Ecology, Vol. 39, No. 4, p. 758, 1958).
Another type of sediment sampler, which circulates acetone, chilled with dry ice, through a probe immersed in a stream bed, requires 11/2 to 2 hours and 12 to 14 Kg. of dry ice to freeze a core 18 to 25 cm. in diameter and 35 cm. long (N. H. Ringlu, Master of Science Thesis, Oregon State University, June 1970).
A piston type device for sampling surface sediments of lake bottom deposits has also been described (S. R. Brown, Ecology 37: 611-613, 1956).
A predecessor of the instant invention was described by me in a U.S.D.A. Forest Service Research Note, PNW-205, August 1973, Forest Service, U.S. Department of Agriculture, Portland, Oregon. This prior art sediment sampler consisted of a 1/2 to 3/4 inch hard-drawn copper pipe 3 feet in length with a point machined from brass soldered to one end and closing the pipe. Another pipe of 3/8 inch soft-drawn copper, cut to reach to the bottom of the first pipe, was connected to a wire reinforced CO.sub.2 delivery hose with brass fittings. The CO.sub.2 delivery hose was connected through a 1/4 inch NPT gate valve to a 15 to 20 pound fire extinguisher bottle. Even with the valve controlling CO.sub.2 delivery through the smaller pipe, obtaining an even flow of gas was difficult, and the smaller pipe would jump out of the larger pipe (i.e., probe) when the valve was opened. It was necessary, therefore, to securely tie down the CO.sub.2 delivery pipe. Also, the difficulty in controlling CO.sub.2 delivery resulted in unequal cooling between samples so that time of sampling, and reproducibility varied substantially.